PIC18F1220_07 Datasheet, PDF (160/308 Pages) Microchip Technology – 18/20/28-Pin High-Performance, Enhanced Flash Microcontrollers with 10-bit A/D and nanoWatt Technology

PIC18F1220/1320
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(AVDD and AVSS), or the voltage level on the
RA3/AN3/VREF+ and RA2/AN2/VREF- pins.
The A/D converter has a unique feature of being able
to operate while the device is in Sleep mode. To oper-
ate in Sleep, the A/D conversion clock must be derived
from the A/D’s internal RC oscillator.
The output of the sample and hold is the input into the
converter, which generates the result via successive
approximation.
FIGURE 17-1:
A/D BLOCK DIAGRAM
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off and any
conversion in progress is aborted.
Each port pin associated with the A/D converter can be
configured as an analog input, or as a digital I/O. The
ADRESH and ADRESL registers contain the result of
the A/D conversion. When the A/D conversion is com-
plete, the result is loaded into the ADRESH/ADRESL
registers, the GO/DONE bit (ADCON0 register) is
cleared and A/D Interrupt Flag bit, ADIF, is set. The block
diagram of the A/D module is shown in Figure 17-1.
10-bit
Converter
A/D
Reference
Voltage
CHS2:CHS0
AVDD
111
110
101
100
VAIN
(Input Voltage)
011
010
001
VCFG1:VCFG0
AVDD
000
x0
VREFH
x1
1x
VREFL
0x
AVSS
AN6⁽¹⁾
AN5
AN4
AN3/VREF+
AN2/VREF-
AN1
AN0
Note 1: I/O pins have diode protection to VDD and VSS.
DS39605F-page 158
© 2007 Microchip Technology Inc.